The present invention relates to vehicle keys, and more particularly, to a key assembly for use in an automobile steering column ignition and lock unit.
Various types of locks for use in connection with the ignition circuit of an automobile are known in the art. Many of such locks include anti-theft and/or anti-tampering mechanisms which are incorporated to deter unauthorized use of automobiles. Increasingly popular with the automotive industry is an electronic interlock operating in connection with the automobile ignition lock. An electronic interlock system uses a coded signal to enable starting of the automobile. Presently, the coded activation signal is read either electronically or optically within the ignition lock, and is subsequently sent to an electronic control module which controls engine operation based on whether a correct signal is received. Hence, an electronic interlock does not allow the lock to be bypassed or "hot wired", or pulled in order to start the automobile. As a result, automobile theft is more time consuming and difficult.
The keys employed with electronic interlock systems contain both mechanical and electronic interlock codes. One such system incorporates the use of a resistor pellet in an ignition key. The pellet provides for a resistor of known resistance so that upon insertion and rotation of the key in an automobile's ignition cylinder unit an electrical current is applied to and through the resistor. A decoding circuit performs a resistance comparison between the resistor in the pellet in the key and a known resistance "window". If the resistance is within the window, the automobile may be started. If the resistance does not match, the automobile will not start. Examples of such interlock systems and keys for use there with are illustrated in U.S. Pat Nos. 4,250,482, 5,083,362, and 5,156,032.
In another electronic interlock system an optical code is employed to control engine operation. Currently, optical codes are in the form of a plurality of hole combinations physically formed in the key. The optical code is formed by utilizing a combination of large and small holes, read by the reader, and subsequently converted into an electronic signal. The activation signal is then sent to the electronic control module of the engine to enable ignition. As a result, a key having an erroneous hole combination will neither enable the ignition system nor start the automobile.
In still another electronic interlock system, there is utilized radio frequency identification (RFID) to enable or disable engine operation. An RFID interlock system consists of a reader which sends a power pulse to an antenna which in turn generates an electromagnetic field. This field energizes a small transponder mounted in the key, which in turn transmits a unique identification code back to the reader via the antenna where it is decoded. If the signal sent by the transponder is a valid identification code, the reader transmits this information to the automobile's electronic control module which in turn enables engine operation. However, if the signal is invalid, the reader transmits this information to the electronic control module which then prevents engine startup. Typically, the antenna generates a relatively high energy RF field which is received by a coil in the transponder, converted to DC voltage and used to supply the transponder's electronic circuitry. The transponder's circuitry in turn transmits its unique identification code in the form of a low energy electromagnetic RF field which is received by the antenna and is in turn decoded by the reader as described above.